1. Field of the Invention
This invention relates to a car air conditioner and, more particularly, it relates to a control circuit for controlling the operation of such an air conditioner.
2. Background Art
A conventional car air conditioner typically has a control arrangement with a configuration as illustrated in FIG. 3 of the accompanying drawings. Referring to FIG. 3, the arrangement for controlling the air conditioner 90 comprises an outlet vent selection switch 91, an air flow rate control switch 92 and an air compressor (AC) switch 93. The outlet vent selection switch 91 has a number of selectable positions including the one for the vent on the dash board and the one for the vent on the foot rest as well as the one for a defroster vent for blowing air onto the front window pane, which is shown as a defroster contact 91a in FIG. 3.
The air flow rate control switch 92 is designed to regulate the number of revolution per unit time of blower motor 94 and hence the flow rate of the air blown out of the outlet vent selected by the outlet vent selection switch 91 and comprises OFF contact 92a, LO contact 92 b, MID contact 92c and MAX contact 92d. The AC switch 93 is used to turn on and off an air compressor (not shown) by way of an air compressor relay 95 and comprises ON contact 93a and OFF contact 93b.
The air flow rate control switch 92 also comprises compressor contact 92e which is disconnected when the switch is turned off. On the other hand, the ON contact 93a of the AC switch 93 is grounded by way of said compressor contact 92e so that the compressor is not operated if the AC switch 93 is turned on unless said blower motor 94 is activated.